Again there's not a lot in it, but there are differences in the noise reduction (since both cameras use the same sensor it's processing we're looking at here). As mentioned elsewhere in this review the A640 output is noisier, but only because the G7 has stronger noise reduction (thanks, presumably to the newer DIGIC III processor). Although the G7 is producing a cleaner result (and one that requires little, if any post-processing), you can see the effect of the noise reduction in places (low contrast, fine detail) - on the A640 image it's just 'grainy', which you may prefer (and of course you can remove noise in post processing, but you can't put detail back in).